<!DOCTYPE html>
<title>
View transitions: Resizing viewport before animating rejects the ready promise.
</title>
<link rel="help" href="https://drafts.csswg.org/css-view-transitions-1/">
<link rel="author" href="mailto:bokan@chromium.org">

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-vendor.js"></script>

<script>
function pollForResize(win) {
  const initial_width = win.innerWidth;
  return new Promise(resolve => {
    const interval_id = win.setInterval(() => {
      if (win.innerWidth != initial_width) {
        win.clearInterval(interval_id);
        resolve();
      }
    }, 100);
  });
}

promise_test(async t => {
  assert_implements(
      document.startViewTransition, 'Missing document.startViewTransition');

  let popup_win;

  // Open a popup window that we'll use to start a transition
  await test_driver.bless('Open a popup in a new window', () => {
      popup_win = window.open('about:blank', 'popup', 'width=300,height=300');
  });

  // Resize the window while the update callback is running (i.e. before
  // capturing the new state).
  let transition = popup_win.document.startViewTransition(async () => {
    // resizeTo is asynchonous so we want to wait until it takes effect
    // before proceeding to capture the new state. Needs to poll for a
    // changed size since rAFs are currently blocked (and thus, so is
    // `resize` event).
    const popup_resize = pollForResize(popup_win);
    popup_win.resizeTo(popup_win.innerWidth/2, popup_win.innerHeight/2);
    await popup_resize;
  });

  // Since the window was resized before capturing the new state, the
  // transition must be skipped and the ready promise rejected.

  let did_finish = false;
  transition.finished.then(() => { did_finish = true; });

  await promise_rejects_dom(t, 'InvalidStateError', popup_win.DOMException,
      transition.ready, 'Resize must must reject `ready`.');

  assert_true(did_finish, 'Transition must be skipped.');
});
</script>
